I can't answer about an MMPORG, but the answer to your first question is very individual. It would depend on whether you (1) want to make 2d or 3d graphics, (2) have good art skills and (3) want a free, middling or expensive graphics program.

There are many 3d models available on the internet, some are free. If you don't want to use them you could possibly adapt them to a figure that you liked somehow.

If you want 2d -- you can use photoshop or draw by hand in a different painting program,

If you have not got good art skills, you might find a friend.

There are very expensive programs for 3d modeling and then there is Blender and Milkshape 3d which are free.